1
BlueMUSE Science workshop
A spectroscopic study of the giant low surface brightness galaxy Malin 1
Junais
Samuel Boissier
Collaborators :
Philippe Amram Benoit Epinat Alessandro Boselli
Barry Madore Jin Koda Armando Gil de Paz
J.C Muñoz-Mateos Laurent Chemin
10 November 2020 2
Low Surface Brightness Galaxies (LSBs)
• Historical definition of LSBs based on disk central surface brightness (Freeman 1970):
Bothun et al. (1997) 3
Low Surface Brightness Galaxies (LSBs)
• Historical definition of LSBs based on disk central surface brightness (Freeman 1970):
• LSBs may account up to 50% of all the galaxies in the universe (Impey & Bothun 1997, Martin et al. 2019)
Bothun et al. (1997) 4
Low Surface Brightness Galaxies (LSBs)
• In recent years, with powerful instruments (e.g. MUSE, Megacam, Dragonfly), there is a new interest in these sources.
• LSBs also similar to galaxies with eXtended UV disk (XUV) (Thilker et al. 2007)
• Ideal laboratories for the study of Star Formation activities in low density regime
• Important to study this large population of galaxies
• Their properties may redefine our knowledge of galaxy formation & evolution
M83 with an XUV Disk 5
Low Surface Brightness Definitions
• « Historical definition » (Freeman 1970)
Diffuse galaxies Disk central surface brightness LSB
• « Diffuse galaxies » (Sprayberry+1995)
• « Ultra Diffuse Galaxies » (Koda+ 2015)
UDG
Hagen et al. (2016) 6
Low Surface Brightness Definitions
• « Historical definition » (Freeman 1970)
Diffuse galaxies Disk central surface brightness LSB
• « Diffuse galaxies » (Sprayberry+1995)
• « Ultra Diffuse Galaxies » (Koda+ 2015)
UDG
Malin 1
Hagen et al. (2016) MALIN 1 77
An extreme case of LSB !!
Malin 1 image credits : NGVS u, g, i MALIN 1 88
Bothun et al. 1987
An extreme case of LSB !! MALIN 1 99
~ 200 kpc diameter
Bothun et al. 1987
An extreme case of LSB !! MALIN 1 10
~ 200 kpc diameter
M33
MilkyWay
Bothun et al. 1987
An extreme case of LSB !! M83 11
A new spectroscopic study of Malin 1
Junais et al. 2020, A&A, 637, A21
Longslit data from Magellan – IMACS Spectrograph
Observations in 2016 and 2019
4 slit positions => 2.5'' slit-width (2016);
1 slit position => 1'' slit-width (2019) 12
Extracted Spectra
Hα
• Spectrum extracted for 16 different regions of Malin 1
• Focussed on the Hα and [OII] emission lines => strongest of all [OII]3726,3729
• Measured quantities :
○ Wavelength shift (Hα and [OII] )
○ Line Flux (Hα) 13
Extracted Spectra
Hα
• Spectrum extracted for 16 different regions of Malin 1
• Focussed on the Hα and [OII] emission lines => strongest of all [OII]3726,3729
• Measured quantities :
○ Wavelength shift (Hα and [OII] ) Rotational velocity
SFR ○ Line Flux (Hα) 14
Malin 1 Hα Rotation Curve
• First time to observe a steep rise in the rotation curve for Malin 1 up to ~400 km/s (inside ~10 kpc) • Created a new mass model based on the new rotation curve. • In the inner regions dynamics may be dominated by the stars (but our models couldn’t explain the highest velocities) • At large radii a massive dark matter halo remains necessary. • We need better quality data (e.g. IFU) 15
Star Formation Rate (SFR) Estimate
• Estimated the local SFR surface density (ΣSFR) from the Hα line flux
• Steep decrease in ΣSFR with radius similar to stellar profile
• Inner region (< 1 Re) : consistent with an early type spiral (S0/Sa)
• Outer region (> 1 Re) : similar to level found in XUV galaxies
(The blue dashed line and shaded
region indicates the typical ΣSFR level found in the disk of XUV galaxies; Bigiel+2010)
Adopted effective radius of Malin 1 = 4 kpc
Gonzalez et al. 2016, Bigiel et al. 2010 16
Work on Malin 1 : Conclusion
● Major result : Steep inner rise of Malin 1 rotation curve
● First SFR order of magnitude estimate for Malin 1 using Hα
● A better determination of dynamics and SFR of Malin 1 clearly requires large-IFU observations.
● Malin 1 was recently accepted for MUSE observation (PI-Gaspar Galaz, rank B observation in the cycle of 2021)
● With BlueMUSE, it would be possible to include most parts of the galaxy in a single pointing when four pointings are needed with MUSE.
● Similar study could be extended to other LSBs & XUVs in a broader context with Malin 1 as a prototype. 17
Need for BlueMUSE
● BlueMUSE will revolutionize the study of LSB universe !
● Its larger FoV and high spectral resolution well suited for LSB observation ○ Reduce observing time ○ Known GLSBs and XUVs are in general ≳1 arcmin (Thilker+07, Boissier+08)
● Observe key emission/absorption lines that are of utmost importance to understand the nature and origin of these galaxies.
➔ Oxygen lines: ◆ Metallicity indication → Explain formation scenarios of GLSBs and XUVs ❏ Low metallicity → Large angular momentum disk (Boissier+2016) ❏ High metallicity → Head-on collision (Mapelli+2008)
➔ Hβ line: ○ Attenuation (Balmer ratio) → LSBs generally considered with low amount of dust (Hinz+07) ○ UV/Hβ ratio → Time delay between star forming events (Boselli+09) → Massive end slope of IMF (ratio of O stars to B stars; Koda+12) ○ SFR on short timescale (10 Myr)
● High resolution 2D kinematics → Dark Matter content → Effect of bars/asymmetries → Signs of accretion/gas removal (formation history) 18
THANK YOU 19 20
Extra slides 21
All Spectra 22
Central Spectrum 23
Mass Model 24
Proposed MUSE fields of Malin 1
White contours are from GALEX UV (Boissier+16) 25
Abundance Ratio
• [N II]6584/Hα ratio --> Abundance estimator (Denicolo et al. 2002)
• Observed high abundance at inner regions of Malin 1
• Could also be due to AGN activity
• Boissier '16 model for Malin 1 predicts low abundance – only for outer disk
• Need to make model for inner regions 26
Dust Attenuation
• Hα/Hβ ratio --> Highly sensible to dust attenuation
• Observed high Hα/Hβ ratio at inner regions of Malin 1
• Applied a standard Equivalent width correction for underlying stellar absorption.
• Indicates low or no amount of dust in Malin 1 27
A new interest for Malin 1 & other giant LSBs
• Deep optical images of Malin 1 reveal new features – Galaz et al. 2015
• The properties of the Malin 1 galaxy giant disk - Boissier et al. 2016
• Formation of a Malin 1 analogue in IllustrisTNG by stimulated accretion - Zhu et al. 2018
• GMRT HI study of giant low surface brightness galaxies – Mishra et al. 2016
• On the classification of UGC 1382 as a giant low surface brightness galaxy – Hagen et al. 2016 Galaz et al. 2015 • UGC 1378 : a Milky Way-sized galaxy embedded in a giant low-surface brightness disc – Saburova et al. Magellan Telescope g and r bands: 2019 • Spiral structure • Diffuse (tidal ?) regions • Massive Low Surface Brightness Galaxies in the EAGLE Simulation – Kulier et al. 2019 28
A new interest for Malin 1 & other giant LSBs
• Deep optical images of Malin 1 reveal new features – Galaz et al. 2015
• The properties of the Malin 1 galaxy giant disk - Boissier et al. 2016
• Formation of a Malin 1 analogue in IllustrisTNG by stimulated accretion - Zhu et al. 2018
• GMRT HI study of giant low surface brightness galaxies – Mishra et al. 2016
• On the classification of UGC 1382 as a giant low surface brightness galaxy – Hagen et al. 2016 Boissier et al. 2016
• Surface brightness profiles of Malin 1 up • UGC 1378 : a Milky Way-sized galaxy embedded in a to 150 kpc in 6 photometric bands giant low-surface brightness disc – Saburova et al. 2019
• Massive Low Surface Brightness Galaxies in the EAGLE Simulation – Kulier et al. 2019 29
A new interest for Malin 1 & other giant LSBs
• Deep optical images of Malin 1 reveal new features – Galaz et al. 2015
• The properties of the Malin 1 galaxy giant disk - Boissier et al. 2016
• Formation of a Malin 1 analogue in IllustrisTNG by stimulated accretion - Zhu et al. 2018
• GMRT HI study of giant low surface brightness galaxies – Mishra et al. 2016
• On the classification of UGC 1382 as a giant low surface brightness galaxy – Hagen et al. 2016
• UGC 1378 : a Milky Way-sized galaxy embedded in a giant low-surface brightness disc – Saburova et al. 2019
• Massive Low Surface Brightness Galaxies in the Boissier et al. 2016 EAGLE Simulation – Kulier et al. 2019 • Predictions for stellar mass, age, metallicity 30
A new interest for Malin 1 & other giant LSBs
• Deep optical images of Malin 1 reveal new features – Galaz et al. 2015
• The properties of the Malin 1 galaxy giant disk - Boissier et al. 2016
• Formation of a Malin 1 analogue in IllustrisTNG by stimulated accretion - Zhu et al. 2018
• GMRT HI study of giant low surface brightness galaxies – Mishra et al. 2016
• On the classification of UGC 1382 as a giant low surface brightness galaxy – Hagen et al. 2016
• UGC 1378 : a Milky Way-sized galaxy embedded in a giant low-surface brightness disc – Saburova et al. 2019
• Massive Low Surface Brightness Galaxies in the EAGLE Simulation – Kulier et al. 2019
Zhu et al. 2018 31
IMACS Specifications 32
Emission Lines
Hα Hβ 33
Absorption Lines
Mg I (5175) Na I 34
Existing Models 35
Malin 1 surface brightness profile
Data Source : Lelli et al. 2010